Some known vehicle systems include multiple vehicles that travel together along a route. For example, rail vehicle consists may include two or more locomotives and one or more railcars connected together. The vehicle systems may have engines that consume fuel and air (e.g., oxygen) to generate propulsive force and travel in open areas having sufficient oxygen supply and ventilation to allow engines of the vehicle systems to provide full power output (e.g., for the horsepower ratings of the engines).
However, these vehicle systems also may travel through areas where there is insufficient available oxygen supply and/or ventilation. For example, during travel in a tunnel, there may be insufficient oxygen available for combustion by the engines of the vehicle systems. If one or more vehicles having the engines are traveling behind one or more other vehicles generating exhaust, the engines in the trailing vehicles may intake the exhaust into the engines instead of oxygen. The lack of ventilation also results in an increased ambient temperature within the area, and the increased ambient temperature limits the amount of heat that can be rejected from a vehicle system traveling through the area. Because of the decreased oxygen, the intake of exhaust, and/or the reduced heat dissipation, the engines may overheat and/or produce less power. For example, the operating temperatures of the engines may increase such that the vehicles automatically decrease the output of the engines.
Some other known vehicle systems are electric vehicles powered by electric current. These systems may be powered by an onboard energy storage source (e.g., batteries) and/or off-board sources of current (e.g., catenaries and/or powered rails). However, the electric circuits can require airflow to cool components of the circuits (e.g., inverters, transformers, and the like). Without sufficient airflow, components of the circuits can overheat over time. For example, during travel in a tunnel, there may be insufficient airflow to adequately cool transformers, inverters, and the like of the circuits onboard the vehicles. As a result of the restricted airflow, the power output of the vehicles and/or time during which the vehicles may operate can be limited.
The decrease in power generated by the engines can cause the vehicle system to slow down and/or stop in the tunnel. Additionally, the length of tunnels may be limiting due to the inability of the engines and/or circuits to operate for extended periods of time within the tunnels. A need exists for methods and systems for controlling vehicle systems in tunnels or other areas where airflow is limited so that the vehicle systems travel through the tunnels faster and/or without stalling.